Secondary memories

Computer is a common household device nowadays. Cost of computer reduced to 10% of the initial cost in last 20 years. Memory storage is the main component of any computer and hence research is progressing for fabricating a low cost memory element. The non-volatile magnetic memory devices are widely used nowadays. There exist 3 categories here- floppy disks, hard disks and magnetic tape. The floppy disk which is also known as diskette is almost lost its importance now. Diskette is used as a magnetic medium for the mass storage of data and programs. It is made of circular-flat piece of plastic material on which iron oxide is coated. Iron oxide is the recording substance. Floppy disks are inexpensive and erasable. Information is recorded on the floppy disks in concentric circles called tracks. CD-ROM is a disk made up of a resin such as polycarbonate. It is coated with aluminium. CD-ROM has high storage capacity. WORM stands for Write Once Read Many and is an optical disk memory. Hard disk contains an assembly of many magnetic disks.